Spark plug



Nov. 7, 1944. BEL 2,361,975

SPARK PLUG Filed Aug. 14, 1941 fig. 2.

l'mventor Patented Nov. 7, 1944 UNITED sures PATENT OFFICE Application Allmt 406,765

2 Claims.

This invention relates to spark plugs for internal combustion engines.

One object of this invention i to provide a spark plug which is adapted to be used in modern high compression internal combustion engines, with a reduced tendency toward fouling and buming out of electrodes.

Another object is to provide a spark plug par ticularly suited for insertion in small-diameter threaded spark plug bores in the cylinder heads of modern internal combustion engines of high compression.

Another object is to provide a spark plug having a sparking chamber with a restricted entrance opening into the explosion chamber of the engine, the electrodes being spaced away from this entrance so as to reduce the fouling and burning out of electrodes.

Another object is to provide a shell for receiving a spark plug of a relatively large diameter base and insertable in a cylinder head bore of smaller diameter so as toiorm a sparking chamher with a restricted entrance with electrodes located a considerable distance from the entrance to the explosion chamber of the engine.

In the drawing:

Figure 1 is a front elevationipartly broken away) in central vertical section, of a spark plug according to a preferred embodiment of this invention.

Figure 2 is a side elevation, partly in section, of the lower shellof the spark plug shown in Figure 1.

Figure 3 is a top plan viewof the lower spark plug shell shown in Figure 2.

In general, the spark plug of this invention consists of a lower shell threaded into a relatively small bore in the engine cylinder head and expandinginto a larger diameter sparking chamber containing the two electrodes of the spark plug, the outer electrode being attached to the upper shell which is threaded into the lower shell and the central-electrode being carried by and extending through the center of the usual insulator or porcelain. In this manner the electrodes of the spark plug are located at a con siderable distance from the explosion chamber and hence are less subject to the entrance heatthe bore I5 is relatively small compared with the the circulation or cooling fluid and having an diameter of the main body 20 of the lower shell l9 and is provided with a bore 2| of restricted diameter opening into a threaded bore 22 of considerably larger diameter within the main body 20 and separated therefrom by a flaring wall 23. The upper end of the lower shell I9 is provided with a hexagonal head 24 to which a wrench may be attached. The main body 20 and lower end portion II are separated from one another by an annular stepped portion 25.

Threaded into the relatively large threaded bore 22 is the threaded lower end 26 of the upper spark plug shell 21, leakage being prevented [by a hollow gasket 28 containing asbestos or other sealing material 29. The upper shell 21 is provided with a central bore 30 expanded at its upper end (not shown) to receive the spark plug insulator 3| or porcelain.

The insulator ll is secured within the upper shell 21 by the knurled or spun portion 22 andis provided adjacent the latter with a hexagonal head 33 for receiving a wrench. The insulator Si i provided with a central bore (not shown) through which passes the central electrode 34.

Arranged adjacent the lower end 40 of the central electrode 34 is the outer electrode 4| which is secured in the lower end 42 of the upper shell 21. The outer electrode I may be secured with a radial hole in the lower end 42 of the upper shell 21 or in any other suitable manner. Thus the electrodes 4| and 34 are located in a relatively large diameter sparking chamber 43 formed by the threaded bore 22 and the flaring wall 23 and with a restricted entrance formed by the bore 2| of the lower end ll of the lower shell It.

In operation, the spark coil or other source oi high tension electricity has 7 one of its leads grounded to the frame or engine in such a manner that it is in circuit with the engine cylinder head ll, whereas the other lead is connected to the central electrode 34 by means of the nut it.

usual threaded disk 31, cap 38 and threaded nut is, or course, employed in connection with distributing theelectricity and timing the various sparks. When the circuit leading to the electrodes 34 and 4! is closed, a spark leaps across the gap between the lower end 40 of the central electrode 34 and the outer electrode 42. This spark takes place within the large diameter chamber 43 which is already filled with explosive gas entering this chamber by means of the restricted port or bore 2| leading through the small diameter portion l8.. The spark ignites the explosive gas within the chamber 43 and the flame thereof shoots through the bore 2! into the explosion' chamber of the engine, igniting the entire charge.

As the ignition takes place within the sparking chamber 43 at a distance from the main explosive chamber 44 beneath the cylinder head ill, the electrodes 34 and 4| are protected from the heat of the main explosion and are also protected from fouling by the products of combustion within the main chamber. It has been iound by actual running tests with the spark plugs constructed according to the present invention that the plugs continue to perform satisfactorily long after the ordinary spark plugs have been rendered inefilcient by fouling or burning out of the electrodes. The ordinary plug, it will be understood, has its central electrode projecting down into the space adjacent the lower end of the portion [8, whereas the outer electrode extends inwardly from a point adjacent the bottom thereof. In such positions, the electrodes of the prior art plug are exposed to the full force of the fiame of the main explosion and also to the products of combustion, burning oil, and other gases or materials tending either to burn out the electrodes or foul them.

In the preferred form of the invention, the

spark plug has been disclosed as made up of upper and lower shells 21 and i9 respectively threaded together, this form of construction being used merely because of convenience in manufacture and for ease in inserting and locating the electrodes 52 and 34. It will be understood, however, that the upper and lower shells 21 and l 9 may be combined in one single shell, the electrodes 4i and 34, however, being located at the same relative positions as in the two-part construction shown in Figure 1.

While a specific embodiment of the invention has been described and illustrated, it will be understood that various modifications may be made within the scope of the appended claims without departing from the spirit of the invention.

' The usual suitable timing and distributing device What I claim is:

l. 'A spark plug or the character described comprising a hollow shell having an external threaded end portion or reduced size capable of being received in a miniature spark plug receiving bore 01' an engine, said reduced portion having a bore of restricted diameter and said shell having an upper internally threaded chamber of enlarged diameter adapted to receive a threaded electrode shell 01' increased size, an insulator extending into said upper chamber, a first electrode extending through said insulator and terminating a distance short of the open end of the threaded electrode shell, and a second electrode extending from said electrode shell within the confines of the open threaded end thereof and projecting beneath said first electrode, said electrode being located and spaced remote from the entrance to said restricted diameter end portion and said electrode shell having an outer diameter contiguous with the outer di ameter of the hollow shell.

2. A spark plug or the character described comprising a hollow shell having an end portion of reduced diameter adapted to be received in a miniature spark plug opening of an engine, said shell at the reduced end portion being provided with a bore of restricted diameter and an upper chamber of enlarged diameter, said upper chamber having an internally screw threaded bore extending inwardly from its open end' to the bore of restricted diameter and said reduced end being externally screw threaded with screw threads of reduced size, an electrode supporting shell having an externally threaded reduced portion adapted to be received in the internally threaded portion of the upper chamber or enlarged diameter, an insulator carried by the electrode supporting shell extending into said upper chamber of enlarged diameter, a first electrode carried on the lower end of said electrode supporting shell, a second electrode carried by the electrode supporting shell and extending through said insulator into the upper chamber and terminating a distance short of the end of said electrode supporting shell directly above said first electrode, said hollow shell comprising a tubular member having a polygonal shaped upper end portion contiguous with the outer diameter of the electrode supporting shell and said electrode supporting shell having a polygonal shaped upper end portion to facilitate the insertion and removal of said electrode supporting shell with respect to said hollow shell.

MURRAY J. SOBEL. 

